Abstract

In this paper we report the effect of solar events (CMEs and solar winds) on foF2 diurnal profiles at Korhogo Station (Long 8.427° W; Lat: 9.336° N; dip: -1.88°) from 1992 to 2002. We reviewed on seasons and all the four geomagnetic activity classes (Quiet activity, recurrent activity, Shock activity, and Fluctuating activity). The results show that (1) Coronal Mass Ejections (CMEs) and high-speed solar winds affect trough around midday on foF2 profiles during winter and spring when fluctuating solar winds have no effect on this characteristic. (2) In autumn, CMEs and solar winds do not affect the nighttime peak, but in winter CMEs, high-stream solar winds and fluctuating solar winds affect this characteristic of foF2 profile. In spring, only storms generated by CMEs and fluctuating solar winds have an effect on the nighttime peak. (3) Most of the time, the ionospheric storms observed at Korhogo station are positive storms and the CMEs always cause stronger positive storms compared to the solar winds effects. We assume that, these storms are mainly related to the combination of the phenomena of rapid penetration eastward electric and equatorward neutral winds during daytime but at nighttime they are mainly related to neutral winds alone.

Key words: Geomagnetic activity, trough, peak, positive storm, negative storm.